Stress plates or seam plates are used in connection with the retention of roof decking membranes upon roof decking substructures at seam locations defined between separate but adjacent or overlapping roof decking membranes, and are of course well-known in the art. Examples of such seam plates or stress plates are disclosed within U.S. Pat. No. 4,945,699 which issued to Murphy on Aug. 7, 1990, as well as U.S. Pat. No. 4,787,188 which also issued to Murphy on Nov. 29, 1988. As can be appreciated from FIGS. 1,2, and 3A-3C of the drawings, which substantially correspond to FIGS. 4,1, and 3A-3C, respectively, of the aforenoted U.S. Pat. No. 4,945,699 to Murphy, the roof decking substructure is disclosed at 103 and may conventionally be provided with overlying insulation 102.
The insulation 102 is, in turn, adapted to have roof decking membranes disposed thereon in an overlying manner, and at a location or site at which separate and adjacent roof decking membranes are to be in effect seamed together in an overlapping manner, a first underlying roof decking membrane is disclosed at 101 and is adapted to be secured to the underlying deck substructure 103 by means of a screw fastener 107 passing through a seam plate or stress plate 10, while a second roof decking membrane 104 is adapted to be secured in an overlapping manner upon the first underlying roof decking membrane 101 by means of a welded seam 111. The seam plate or stress plate 10 is seen to have a circular configuration, and is provided with an upper surface 11 and a lower surface 12. A central aperture 15 is provided for passage therethrough of the screw fastener 107, and a circular reinforcing rib 14 annularly surrounds the central aperture 15.
Accordingly, when such a stress plate or seam plate 10 is to be used to secure roof decking membranes to the underlying decking substructure 103, the stress plate or seam plate 10 is disposed atop the first underlying roof decking membrane 101, and the stress plate or seam plate 10 is then fixedly secured to the underlying decking substructure by means of screw fastener 107 being threadedly engaged with the underlying decking substructure. In accordance with the particularly unique stress plate or seam plate 10 as disclosed within the noted Murphy patents, the bottom surface 12 of the stress plate or seam plate 10 is provided with a plurality of circumferentially spaced prongs or tangs 21 each of which terminates in a gripping point 22. The prongs or tangs 21 each have a substantially triangular configuration and are in effect partially punched-out or otherwise cut from the bottom surface portion 12 of the plate 10, and are subsequently bent such that the prongs or tangs 21 attain their desired disposition with respect to the bottom surface portion 12 of the plate 10. Such prongs or tangs 21 will therefore grip the lower or underlying roof decking membrane 101 and prevent the same from becoming loose or free with respect to the stress plate 10 or the underlying roof substructure 103 despite wind or other environmental forces being impressed upon the roof decking membrane 101.
While the aforenoted stress or seam plates of Murphy have been satisfactory and commercially successful, it has been experienced that, despite well-meaning statements of intent to the contrary as set forth in the Murphy patents, the presence of the pointed prongs or tangs 21 characteristic of the stress plate or seam plate 10 of Murphy do in fact tend to puncture, tear, weaken, and otherwise cause deterioration of the roof decking membranes 101 under wind and other environmental conditions. Obviously, such a state is not satisfactory in view of the fact that eventually, the roof decking membranes tear away from the overlying seam plate 10 as well as away from the underlying roof decking, with the consequent result being the compromise of the structural integrity of the entire roof decking system. Accordingly, the stress or seam plate, as disclosed within U.S. Pat. No. 6,665,991 which issued to Hasan on Dec. 23, 2003, was developed in order to effectively rectify the deficiencies characteristic of the stress or seam plate as disclosed within the aforenoted patent to Murphy. More particularly, as disclosed within FIGS. 4 and 5, wherein FIG. 4 discloses a stress or seam plate 210 generally similar to the stress or seam plate disclosed in FIG. 4 of the Hasan patent, and wherein further, FIG. 5 corresponds to FIG. 7 of the Hasan patent, it is seen that each one of the projections 232 is effectively struck or punched out from the plate 210 so as to comprise side or leg portions 234,236 and a rounded apex portion 238. While the stress or seam plate 210 has been commercially successful and has provided improved service and wear attributes in connection with roof decking structures, as a result of the particular configuration of the projections 232 having effectively resolved the undesirable tearing or puncturing problems encountered or caused by means of the pointed barbs, prongs, or tangs 21 of Murphy, some operational difficulties have occasionally been experienced with the stress or seam plate 210 of Hasan.
For example, as can readily be appreciated from FIGS. 4 and 5, in view of the fact that, as has been noted, each one of the projections 232 has been struck or punched out from the stress or seam plate 210 so as to project downwardly beneath the undersurface portion 250 of the stress or seam plate 210, as defined by means of the side or leg portions 234,236 and the rounded apex portion 238, a substantially rectangularly configured through-aperture 252 is defined within those regions of the stress or seam plate 210 from which the projections 232 have been struck or punched. Accordingly, when a plurality of the stress or seam plates 210 are disposed in contact with each other, such as, for example, in a nested state within packaging, or in a nested state within an installation tool, it is possible that one or more of the stress or seam plates 210 can become interlocked together as a result of the downwardly extending projections 232 disposed upon one of the stress or seam plates 210 being aligned with and entering a corresponding aperture 252 formed within an adjacent stress or seam plate 210. Therefore, when the seam or stress plates 210 are to be removed from the packaging so as to, for example, be deposited within a suitable magazine of an installation tool, the adjacent seam or stress plates 210, which have effectively become stuck together as a result of the aforenoted disposition of one or more of the downwardly extending projections 232 of one of the stress or seam plates 210 having become jammed within a corresponding aperture 252 formed within the adjacent one of the stress or seam plates 210, are difficult to separate. In a similar manner, when the stress or seam plates 210, disposed within the installation tool are to be individually and serially dispensed from the installation tool in connection with the installation of environmental membranes upon a roof decking substructure, the adjacent stress or seam plates 210 which have effectively become stuck together, as a result of the aforenoted disposition of one more of the downwardly extending projections 232 of one of the stress or seam plates 210 having become jammed within a corresponding aperture 252 formed within the adjacent one of the stress or seam plates 210, will not be readily able to be separated and dispensed whereby the installation tool will experience jamming. All of these difficulties will, of course, lead to operational or production downtime whereby personnel will have to expend a substantial amount of time separating the stress or seam plates 210 which have become interlocked together with respect to each other either within the packaging or installation tool, leading to operational or production inefficiencies.
A need therefore exists in the art for a new and improved stress plate or seam plate wherein the stress plate or seam plate can satisfactorily engage the environmental membranes so as to secure the environmental membranes to the underlying roof decking substructure, and yet, the means formed upon the stress plate or seam plate for engaging the environmental membranes will not tend to initiate tearing of the environmental membranes under, for example, windy or other forceful environmental conditions, and still yet further, such stress plates or seam plates will not become interlocked with respect to each other despite the fact that they will be disposed within a nested state.